1. Field of the Invention
The present invention relates to surgical instruments with paired jaws that deliver thermal energy to the engaged tissues to create an effective seal or weld in the tissue. More in particular, the invention applies extremely high compressive forces to engaged tissue together with the application of ultrasonic energy to the tissue from two opposing sides of the tissue to thereby effectively deliver energy to the tissue.
2. Background of the Invention
In various open and laparoscopic surgeries, it is necessary to seal or weld the tissue volumes targeted for transection. Many common procedures require both sealing and transection of tissue, for example, the take-down of gastric arteries in endoscopic Nissen fundoplications, the sealing of tissue margins in lung resections, and the sealing of blood vessels in endoscopic colon surgeries that transect the mesentery. In some such procedures, stapling instruments are used to apply a series of mechanically deformable staples to transected blood vessels or other tissue volumes. The use of such mechanical is time consuming and often will not create an effective seal resulting in leaks that can cause serious complications.
Surgical instruments that utilize ultrasound energy for coagulating, sealing or transecting tissue have been commercialized for use in both open and endoscopic procedures. The ultrasonic instruments that are available suffer from several disadvantages. A typical prior art ultrasonic instrument has (i) a rigid energy-transmitting member that transmits acoustic vibrations from the handle to the working end, and (ii) a moveable jaw member that is used to capture and press the targeted tissue volume against the single energy-transmitting member. (See, e.g., U.S. Pat. No. 5,322,055).
It has been found that prior art ultrasound instruments cannot apply significant compressive forces against tissues to create a reliable, effective weld in many targeted tissuesxe2x80x94particularly in (i) substantially thick anatomic structures; (ii) large diameter blood vessels; (iii) tissue volumes that are not uniform in hydration, density and collagenous content; and (iv) bundles of disparate anatomic structures. It also has been found that prior art ultrasound instruments are inefficient at delivering energy to the above-described targeted tissues since the energy is only delivered from one surface of the engaged tissue. A further disadvantage of commercially available ultrasound instruments is that they cannot easily be reduced in cross-sectional dimensionxe2x80x94which would be useful for less invasive surgeries. The typical prior art instrument has a first elongate energy-transmitting member that extends the length of the instrument plus a second adjacent extension member that comprises linkage for opening and closing the jaw structure. Another disadvantage of prior art ultrasound instruments in lack of functionality with respect to transecting tissue and welding the tissue volume. Typically, the instrument requires reconfiguration of the working end in order to first perform a sealing task and then to perform a transection task, which is inconvenient and time-consuming.
The present invention relates to a surgical instrument that is adapted to transect a targeted tissue volume and contemporaneously weld the margins of the transected tissue. As background, the biological mechanisms underlying tissue fusion by means of thermal effects are not fully understood. In general, the delivery of energy for sealing a targeted tissue volumexe2x80x94no matter the sourcexe2x80x94is adapted to denature proteins, including collagen, into a proteinaceous amalgam that intermixes and fuses together as the proteins renature. As the treated region heals over time, the damaged tissue is partly reabsorbed by the body""s wound healing process resulting in a scar-type tissue or biological weld. In order to create an effective weld in tissue volumes that are not uniform in hydration or collagen content, such as blood vessels with significant fascia layers, it has been found that several factors are critical. First, it has been found that the application of very high compressive forces to the engaged tissue prior to, or contemporaneous with, energy delivery can greatly increase the strength of the weld. It is believed that such very high compressive forces cause more effective entanglement and intermixing of denatured proteins thereby increasing the strength and uniformity of the developing biological weld. It has further been found that effective welds require a uniform selected temperature across the targeted tissue volume for a selected time interval. The working end of the invention utilizes high compressive forces to homogenize the engaged tissue by causing extracellular fluids to migrate away from the engaged tissue to collateral regions to create uniform hydration. In other words, the energy absorption characteristics of the engaged tissue can be made more uniform to allow a more even temperature distribution across the targeted tissue volume to thereby create a uniform weld.
One preferred embodiment of the invention provides an improved system of coupling ultrasound energy to engaged tissue volumes to weld tissue. More in particular, the invention provides an ultrasound transmission unit and elongate waveguide that is reciprocatable in an interior bore of an introducer. Unlike prior art ultrasound instruments, the waveguide of the present invention is not adapted to directly engage tissue. Instead, the elongate waveguide of the invention carries channels with engagement surfaces therein that are adapted to continuously engage cooperating exterior surfaces of first and second jaw elements under very close tolerances. The invention thus provides first and second jaw elements that are part of a tuned acoustic assembly wherein acoustic wave transmission is coupled between the waveguide and the jaws. Thus, the reciprocatable waveguide of the invention is adapted to perform several unique functions: (i) to couple ultrasound energy to both opposing jaws to thereby deliver energy to both sides of the captured tissue to create uniform thermal weld effects; (ii) to apply very high compressive forces to the captured tissue by having the reciprocating member engage the jaws substantially along the entire length of the jaws, and (iii) to transect the captured tissue contemporaneously with the delivery of energy that is adapted to weld the tissue.
Of particular interest, the invention allows the reciprocatable ultrasonic transmission assembly to be easily sterilizable and reusable since it does not directly contact tissues. Such a reusable ultrasonic transmission assembly then can be inserted in a disposable handle-introducer that carries a jaw structure that actually engages the tissue. Further, the use of the reciprocatable ultrasonic transmission assembly as a mechanism for actuating the jaw structure between open and closed positions allows the cross-section of the working end to be scaled down in dimension for less invasive surgeriesxe2x80x94that would not be possible with prior art designs of ultrasound instruments.
In general, the apparatus and method of the present invention advantageously provide means for effectively coupling ultrasonic energy to engaged tissue for purposes of welding tissue.
The present invention advantageously provides a system that allows for ultrasonic energy transmission to both opposing jaw faces of a working end that engages tissue under high compression.
The present invention provides an ultrasonic energy transmission unit that is independent of the opposing jaw surfaces that engage and compress tissue.
The present invention provides a reciprocating ultrasonic energy transmission unit that slidably mates with independent first and second jaw elements that are a part of the tuned acoustic assembly.
The present invention provides a reciprocatable ultrasonic energy transmission unit that is reusable and is adapted for used with a disposable introducer-jaw assembly.
The present invention provides an ultrasonic energy transmission assembly that is reciprocatable with very close tolerances over an independent jaw assembly to provide combined functionality: (i) to deliver ultrasonic energy to the working end, and (ii) to open and close the jaw elements.
The present invention provides an ultrasonic energy transmission unit that can be fabricated in single member to without moving parts that can effectively transmit ultrasonic energy to opposing first and second openable-closeable jaw elements.
The present invention provides a system that can scale the ultrasonic energy transmission unit small diameters when compared to prior art devices.
The present invention provides a reusable ultrasonic energy transmission unit that can be easily fitted with a disposable sharp blade for transecting tissue.
The present invention provides a system for applying extreme compressive forces on capture tissue volume to reduce the tissue cross-section to about 0.001xe2x80x3 to insure uniform energy densities for effective tissue welding.
The present invention provides an ultrasonic energy delivery system that can prevent tissue ablation or desiccation due to excess thermal energy delivery.
Additional objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.